Extraction of oleiferous materials



Patented Aug. 14, 1951 EXTRACTION or OLEIFEROUS! MATERIALS Louis C. Rubin, West Caldwell, N. J., assignor to The M. W. Kellogg Company, Jersey C ty, N. ,L, a corporation of Delaware Application April 23, 1947, Serial No. 743,290

6 Claims.

This invention relates to an improved method for re60vering iatty materials, and similar high molecular weight naterials, from the solid materials with which they are normally associated in nature. Such Q1id materials are referred to hereinafter as oleiferous solid materials. Such oleiferous materials include various oil-bearing beans, seeds and nuts designated generally as oil seeds, and including soybeans, cottonseed, linseed, peanuts, palm nuts and .cocoanuts. Other oil-bearing solid materials of animal, vegetable and marine origin also are included within the term oleiferous solid materials, such as animal tissue, including fish livers, vegetable fibers, nut shells, etc.

The invention relates particularly to extraction processes employing solvents whose boiling points are lower than the preferred temperature of ex? traction. In partieular the invention relates to an improvement in the process of extracting oleiferous materials with relatively low-boiling solvents. Such solvents may be defined as those whose critical temperature is not substantially higher than 450 F. and preferably are lower than 325 F. .Of these, the solvents which are normal- 1y gaseous are preferred because of the relative ease with which they may be separated from the oil and the residual solid material.

The low-boiling hydrocarbons represent .a desirable class of solvents because of their relative inertness and. low cost. While the low-boiling olefin hydrocarbons may be employed they are less desirable than the low-boiling parafiins such as ethane, propane, the butanes, the pentanes and the hexanes, from the point of view of inertness. Of the parafilns, propane is preferred ordinarily because of they high degree of solubility of the oils in that solvent and its relatively low critical temperature which permits operating in a temperature range not injurious to the oils. However, ethane or the butanes can be employed to almost as great advantage. While relatively pure hydrocarbons are preferred mixtures of them may be employed. For example, mixtures of ethane and propane or mixtures of butane and methane may be employed in the proportions suitable to form solvents having the desired properties. While the normally gaseous hydrocarbons are particularly advantageous for use as solvents in the improved method other solvents having relatively low critical temperatures may be employed, such as ammonia, dichlordifluor methane, dimethyl ether, methyl fluoride and halogenated hydrocarbons in general.

The use of such relatively low-boiling solvents requires maintaining the extraction zone under (c1. zoo-412.8)

a substantial superatmospheric pressure to pree t porization of the S l t an e l iv y h h t m a r s ar emp y d i m nvo e an ope atin ssure in t extraction zone of 5,0!) to 10,00 peunds per square inch. In accordance with the improved method of this invention oleiterp s solid materials, to be subjected to the e t ac on treatment n extraction Zone which is maintained under substantial superatmospheric pressure, are first mixed, in a finely vi d e ud tion with 91. pre extracted from similar solid oleiierous material, to form a slurry of the oil'and the solid. The slurry is then pumped into the extraction zone against the pressure thereoi and into contact with the solvent. The oil employed for forming the slurry m y c ns itute a portion of the Whole .oil previously extracted from similar solid material or the slurry oil consist of a traction of such previously extracted oil. The slurry is formed by mixing the oil and solids ,at relatively low pres.- sure, for example atmospheric pressure, and the resulting slurry is then easily transferred by means of a pump :to the zone of higher pressure without danger oi escape of solvent from the ex! traction zone or the introductionof gaseous oxy gen from the atmosphere into the extraction zone.

The invention will be described further, and in more detail, by reference to various specific mQdir fications which are illustrated in the accompany,- ing drawing, which is a schematic representation of apparatus suitable for carrying out such modifications. In the further description of the invention propane will be reierred to as the solvent, but it is ,to be understood that the principles of operation are the same in the use of any of the preferred solvents mentioned above, the operating conditions being changed only in accordance with the character of the .oil to be extracted and the physi al p p rt es .of th solve t.

Referring to the drawing, the principal pieces of equipment, represented are a slurry tank 1, an extractor :2, a prenane stripper 3, a separator 4, a fractionat-ing tower 5, and/a, separator .6. The slurry of oil and .oleiferous solid material is formed in tank 1 and subjected to extraction treatment in extractor The extracted solids are treated for the recovery of propane in separator I, and slurry oil is recovered as a lower phase i sepa a o t we 5 or separator s, an prepared for use by the .eyaporation of residual p pane i s r p er L3 The slurry ,oil is transferred from stripper 3 through line 38 to slurry tanlr J. Finely divided oleiferous material, such as ground 011 seeds, is introduced into slurry tank I from hopper 9 through valve [0. Valve It may be of any suitable construction but conveniently is a star feeder arranged for continuously introducing measured quantities of oleiferous solids into tank I. The slurry is formed and maintained by suitable stirring means I I.

The slurry is continuously pumped through line [2 into an intermediate point of extractor 2. Pump I3 is provided in line l2 for transferring the slurry from the substantially atmospheric pressure of slurry tank I to thesuperatmospheric pressure of extractor 2.

Liquefied propane is introduced continuously into the lower part of extractor 2 through line 14. Extractor 2 preferably is somewhat elongated vertically whereby the solid material introduced through line I2 is permitted to settle through an upfiowing stream of propane over a substantially long path of contact in order to effect the maximum desired extraction of oil from the oleiferous'solids. A substantial space is provided in extractor2 above line l2 to permit maximum settling of solids out of the stream of propane.

Extractor 2 ordinarily is maintained at the temperature of maximum solubility of the oil in the propane in order to provide efiicient extraction. This may vary from about room temperature to 160 F. Consequently the pressure imposed on extractor 2 may vary from about 50 pounds per square inch to about 700 pounds per square inch. The propane may be charged to extractor 2 at a rate equivalent to a ratio of 3 to or more volumes of liquid propane per volume of the, oil to be extracted and the slurry oil introduced through line [2 into extractor 2.

The unextracted solid material is withdrawn from the bottom of extractor 2 through line l5 which connects with separator 1, as a slurry of propane and solids. Pressure is reduced substantially at It whereby the propane is substantially completely evaporated and withdrawn from separator 1 through line H. To assist evaporation heat may be introduced into separator I at [8. To further assist vaporization steam may be injected at IS. The relatively dry solid material, such as seed meal,is withdrawn from the bottom of separator 1 through line [9 by any suitable means, such as a star feeder.

The extract solution is withdrawn from the top of extractor 2 through line which connects with separator 4. In accordance with one modification of the invention the extract solution is subjected to reduced pressure in separator 4 to effect evaporation of propane, which is withdrawn for reuse through line 2|. To assist evaporation heat may be applied to the solution in separator 4, as by heating means 22. The extract oil is withdrawn from the bottom of separator 4 through line 23. A portion of the extract oil flowing through line 23 is diverted through line 24 which connects with stripper 3. In stripper 3 the extract oil is subjected to suitable treatment, as by heat applied through means 25, to vaporize residual propane, which is removed through line 26. The slurry oil thus formed is transferred from stripper 3 through line 8 to slurry tank I, as described.

Any suitable ratio of slurry oil to solids may be employed in forming the slurry, it being understood that it is preferred to employ the smallest ratio necessary to form a pumpable slurry. The minimum ratio necessary will be afiected by the character of the oil and solid and the quantity of oil in the solid, but a weight ratio of oil to solid of at least 1:1 ordinarily is necessary. This refers to solids prepared in the usual manner for extraction by adjusting the moisture content to the optimum level for solvent extraction.

Extract oil withdrawn irom separator 4 through line 23 may be transferred, through line 21, to an intermediate point in a fractionating tower 5 in which the oil is subjected to suitable fractionation treatment by countercurrent contact of the oil with an upflowing stream of additional liquid propane, which is introduced into the lower part of tower 5 through line 28. Tower 5 is operated at a temperature, set by the temperature of the propane introduced through line 28, in the temperature range in which solubility of the oil in the propane decreases with rising temperature. This range extends from a few degrees above the critical temperature to approximately F. below the critical temperature. For propane the usual operating temperature range for tower 5 is from about F. to 210 F. although slightly higher or lower temperatures may be employed under certain circumstances. In tower 5 the extract oil from line 2! is subjected to countercurrent extraction as the oil flows downwardly as a heavy liquid phase in contact with the upfiowing propane or extract phase. The extract is subjected to rectification treatment in tower 5 above line 21 by heating the extract to a higher temperature, by heating means 29, or by refluxing the tower with extract from line 30, or by both means.

By suitable control of temperature conditions in tower 5 the extract oil may be closely fractionated ,and distributed between the extract and the rafiinate in any desired manner. The fraction recovered in the extract phase is composed of constituents having a relatively low molecular weight, whereas the rafiinate is composed of constituents having a relatively high molecular weight. The rafinate is withdrawn from the bottom of tower 5 through line 3! and the extract phase is withdrawn overhead through line 32. Line 32 connects with separator 6 in which the pressure on the extract phaseis substantially reduced to permit evaporation of propane which is withdrawn overhead for reuse through line 33. Heat may be applied in separator 6- to assist vaporization. The extract oil fraction thus recovered in separator 6 is withdrawn therefrom through line 34. A portion of this extract oil may be employed to reflux tower 5 and for this purpose line 30, provided with a pump 35, connects line 34 with the upper part of tower 5. Tower 5 is substantially elongated vertically and is suitably provided with contact means to assist in effecting intimate contact of the counter-flowing liquid phases.

In accordance with another modification of the invention the slurry oil is provided by diverting a portion of the relatively low molecular weight extract oil fraction from line 34. For this purpose line 36 is provided to connect line 34 with stripper 3. In this modification line 23 is not employed, and the oil introduced into stripper 3 through line 36 is treated'in the manner previously described to provide the slurry oil for passage through line 8. This modification is advantageous in that the quantity of oil necessary to form a slurry is reduced and the burden placed on the extractor 2 by the slurry oil is minimized since the relatively low molecular weight extract oil fraction is relatively more soluble in the propane solvent.

In accordance with another modification of the invention rafii nate from line 3| may be employed as' a source of the slurryoil. For this purpose line 31 is provided to connect line 8! with stripper 3.

In accordance with another modification of the invention the extract solution emerging from extractor 2 through line 28 may be treated without vaporization of propane to separate a fraction of the oil content thereof for use as slurry oil. In this modification the extract solution is heated in line 26, or in separator 4, to a temperature above the temperature of maximum solubility of the oil in the propane to precipitate a, separate oil phase, while maintaining the extract solution under a pressure effective to prevent substantial vaporization of the propane. The-extract solution is heated to a temperature, ordinarily within the range of 146 to 180 F., to precipitate a portion of the oil sufiicient in volume toprovidethe required amount of slurry oil. A pump 38 is provided in line as to introduce the extract solution in separator 44 against the high pressure necessary in this modification. The heating of the extract solution according to this modification lowers the solubility of the oil in the propane and causes a portion of the oil to precipitate. and form a separate, lower, liquid phase. The lower phase includes some propane but in a propane: oil ratio much lower than the corresponding ratio in the extract solution.

The lower phase material is transferred from separator 4 through lines 23 and 2 3 to propane stripper 3, while the upper liquid phase is withdrawn from separator 4 for father treatment in any suitable manner. For example, the oil content of the upper phase from separator 4 may be separated from the propane inseparate separation means similar to separator i and the 011 thus obtained passed to fractionating tower 5 for further treatment in a manner similar to the first-described modification of the process of the invention.

Alternatively, the extract solution may be heated in separator 4 to a temperature suificiently high to precipitate all, or substantially all, of the oil contained in the extract solution. In this operation the resulting upper phase contains nearly all of the propane and at most a relatively small amount of th oil, while the lower phase contains most of the oil and a small amount of the propane. In accordance with this modification a portion of the lower phase may be passed to stripper 3 to produce slurry oil, in the manner described, while the remainder is passed through line 21 to an intermediate point of tower 5. The upper phase liquid, consisting of propane, is passed from separator 4 through lines 2| and 39 to a relatively low point of tower 5. If necessary, a pump 48 is provided in line 3&3. Cooling or heating means are provided in line 39 at 4| to adjust the temperature of the propane phase to the operating level desired in tower 5. By this method the lower phase material from separator 4 is subjected to stripping in tower 5 by the propane phase from line 39. Additional propane is introduced as necessary through line 28 to assist in the stripping action.

In accordance with a further modification of the invention the extract solution emerging from extractor 2 through line 23, or the upper phase material emerging from separator 4 after the precipitation of a part of the oil to obtain a slurry'oil, is transferred directly to tow-er 5 for rectification and fractionation. This operation is carried out in the absence of any material introduced into tower 5 through line 21. If the extractsolution is first heated in separator 4 to obtain a slurry oil precipitate, the remaining extract solution is passed through lines 2| and 33 to tower 5 in the manner described. For transferring the extract solution directly from line 20 to tower 5, line 52 is provided to connect line 25 with line 39. The extract solution is thus passed from a low point in tower 5 upwardly through the tower in countercurrent contact with a downwardly flowing oil. phase produced in the tower by imposing a higher temperature on the top of the tower, as by heating means 29, and by refluxing the tower with extract from line 36. The extract solution is thus subjected to rectification and fractionation with the formation of separate fractions which are recovered at 34 and 3|. The lower liquid phase fiows downwardly through tower 5 and may be subjected to final stripping by means of propane from line 28'.

Slurry oil from separator 4, tower 5' or separator 6 may be obtained in connection with any of the foregoing modifications of the invention. When the slurry oil is obtained by heating the extract solution to a high temperature under pressure in separator t the finely divided. solid material which is inevitably suspended in the liquid stream flowing out of the extractor 2 through lin 20' is occluded in the droplets of lower phase liquid precipitated in separator 4. By this means-the fines from the extractor are separated from the extract oil without filtration. This likewise applies to the operation of tower 5 to obtain a raffinate which is to be used as the slurry oil.

I claim:

1. A method for treating ole'iferous solid materials with solvent in an extraction zone to obtain an oil extract from said solid material which comprises introducin into the extraction zone a solvent whose boiling point is lower than the temperature of extraction, maintaining said extrac tion zone at the extraction temperature and under a superatmospheric pressure efiective to maintain the solvent in liquid condition, mixing said solid material in a finely divided condition at a point external of said extraction zone with a slurry oil comprised of components of said oil extract to form a slurry, pumping said slurry into said extraction zone against the pressure thereof and into contact with said solvent, withdrawing an extract solution containing said oil extract from said extraction zone, separating from said extract solution at least a fraction of said extract oil, and recycling said extract oil to said slurry-forming step to serve therein as said slurry oil.

2. The method of claim 1 in which a normally gaseous solvent is employed.

3. The method of claim 1 in which a normally gaseous hydrocarbon solvent is employed.

4. A method for treating a charge material comprised of naturally occurring non-fatty solvents containing intimately associated fatty material with solvent in an extraction zone to obtain an oil extract from said solid material which comprises introducin a normally gaseous solvent into said extraction zone, maintaining said extraction zone under superatmospheric pressure effective to maintain the solvent in liquid condition, mixing said solid material in a finely divided condition at a point external to said extraction zone with a slurrry oil comprised of components of said oil extract to form a slurrry, pumping said slurry into said extraction zone against the pressure thereof and into contact with said solvent, separating an extract solution containing said 011 extract from said solid material, fractionating said oil in the presence of said normally gaseous solvent to separate the oil into a plurality of fractions, and. recycling at least a portion of a fraction thus obtained to said slurry-forming step for admixture with more of said charge material to form a slurry, in the manner described.

5. In the extraction of an oil extract from a charge material comprised of naturally occurring non-fatty solids containing intimately associated fatty material by treatment with a normally gaseous solvent, the improved method which includes the steps of reducing said charge material to a finely divided condition and forming a pumpable slurry by mixing said finely divided charge material with at least an equal amount of slurry oil comprised of components of said oil extract; pumping said slurry into an extraction zone under a pressure sufiiciently high to maintain said solvent in a liquid condition; contacting said slurry with said solvent in said extraction zone to dissolve said oil extract in an extract solution including some suspended fines; withdrawing said extract solution from said extraction zone and increasing the temperature of said solution to a temperature in the range of temperatures near the critical temperature of the solvent in which solubility decreases as temperature increases, said temperature being sufliciently high in said range to precipitate a relatively heavy lower phase fraction occluding suspended fines; withdrawing said lower phase fraction together with suspended fines and stripping solvent therefrom; and recycling said stripped fraction to said slurry-forming step to be used therein as said slurry oil and to return fines which had been suspended in the extract solution to said extraction zone.

6. In the paracritical fractionation of an oil extract from a charge material comprised of naturally occurring non-fatty solids containing intimately associated fatty material by treatment with a normally gaseous solvent, the improved method which includes the steps of reducing said charge material to a finely divided condition and forming a pumpable slurry by mixing said finely divided charge material with at least an equal amount of slurry oil comprised of components of said oil extract; pumping said slurry into an extraction zone under a pressure sufficiently high to maintain said solvent in a liquid condition; contactin said slurry with said solvent in said extraction zone to dissolve said oil extract in an extract solution; withdrawing said extraction solution from said extraction zone and paracritically fractionating said extract solution with said solvent at temperatures in the range of temperatures near the critical temperature of the solvent in which solubility decreases as temperature increases; withdrawing one of said fractions and stripping solvent therefrom; and recycling said stripped fraction to said slurry-forming step to be used therein as said slurry oil.

LOUIS C. RUBIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,494,090 Wilson May 13, 1924 1,849,886 Rosenthal Mar. 15, 1932 2,118,454 Schaafsma May 24, 1938 2,152,667 Rosenthal Apr. 4, 1939 2,183,837 Hamilton et a1 Dec. 19, 1939 2,270,674 Pilat et al Jan. 20, 1942 2,281,865 Van Dyck May 5, 1942 2,416,196 Mortenson Feb. 18, 1947 

1. A METHOD FOR TREATING OLEIFEROUS SOLID MATERIALS WITH SOLVENT IN AN EXTRACTION ZONE TO OBTAIN OIL EXTRACT FROM SAID SOLID MATERIAL WHICH COMPRISES INTRODUCING INTO THE EXTRACTION ZONE A SOLVENT WHOSE BOILING POINT IS LOWER THAN THE TEMPERATURE OF EXTRACTION, MAINTAINING SAID EXTRACTION ZONE AT THE EXTRACTION TEMPERATURE AND UNDER A SUPERATMOSPHERIC PRESSURE EFFECTIVE TO MAINTAIN THE SOLVENT IN LIQUID CONDITION, MIXING SAID SOLID MATERIAL IN A FINELY DIVIDED CONDITION AT A POINT EXTERNAL OF SAID EXTRACTION ZONE WITH A SLURRY OIL COMPRISED OF COMPONENTS OF SAID OIL EXTRACT TO FORM A SLURRY, PUMPING SAID SLURRY INTO SAID EXTRACTION ZONE AGAINST THE PRESSURE THEREOF AND INTO CONTACT WITH SAID SOLVENT, WITHDRAWING AN EXTRACT SOLUTION CONTAINING SAID OIL EXTRACT FROM SAID EXTRACTION ZONE, SEPARATING FROM SAID EXTRACT SOLUTION AT LEAST A FRACTION OF SAID EXTRACT OIL, AND RECYCLING SAID EXTRACT OIL TO SAID SLURRY-FORMING STEP TO SERVE THEREIN AS SAID SLURRY OIL. 